Antisense technology is an effective means for reducing the expression of one or more specific gene products and can therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications. Chemically modified nucleosides are routinely used for incorporation into antisense compounds to enhance one or more properties, such as nuclease resistance, pharmacokinetics or affinity for a target RNA. In 1998, the antisense compound, Vitravene® (fomivirsen; developed by Isis Pharmaceuticals Inc., Carlsbad, Calif.) was the first antisense drug to achieve marketing clearance from the U.S. Food and Drug Administration (FDA), and is currently a treatment of cytomegalovirus (CMV)-induced retinitis in AIDS patients. More recently, Kynamro™ (Mipomersen sodium injectable; developed by Isis Pharmaceuticals Inc., Carlsbad, Calif.) has achieved marketing clearance (2013) from the U.S. Food and Drug Administration (FDA), and is currently a treatment of homozygous familial hypercholesterolemia (HoFH).
New chemical modifications have improved the potency and efficacy of antisense compounds, uncovering the potential for oral delivery as well as enhancing subcutaneous administration, decreasing potential for side effects, and leading to improvements in patient convenience. Chemical modifications increasing potency of antisense compounds allow administration of lower doses, which reduces the potential for toxicity, as well as decreasing overall cost of therapy. Modifications increasing the resistance to degradation result in slower clearance from the body, allowing for less frequent dosing. Different types of chemical modifications can be combined in one compound to further optimize the compound's efficacy.
The diastereoselective synthesis and characterization of dinucleotides containing a cyclic phosphate or cyclic phosphonate internucleoside linkage have been reported (see Clezio et al., Organic Letters, 2003, 5(2), 161-164 Dupouy et al., Eur. J. Org. Chem., 2006, 5515-5525; and Catana, et al., Eur. J. Org. Chem., 2011, 34, 6857-6863).
The synthesis of DNA dinucleotides containing a cyclic phosphate internucleoside linkage has been described (see Clezio et al., Eur. J. Org. Chem., 2007, 1935-1941).
The synthesis of dinucleotides including 2′-H, 2′-OH and 2′-OCH3 modified nucleosides and containing a cyclic phosphate internucleoside linkage has been described. The dimers were analyzed by X-ray crystallography and NMR spectroscopy (see Maturano et al., Eur. J. Org. Chem., 2012, 4, 721-730).
The diastereoselective synthesis and characterization of tetranucleotides containing a cyclic phosphate internucleoside linkage have been reported (see Clezio et al., Eur. J. Org. Chem., 2007, 3894-3900).
The introduction of α,β-D-CNA (constrained nucleic acid) within oligonucleotides has previously been shown to stabilize the duplex DNA (see Dupouy et al., Organic & Biomolecular Chemistry, 2008, 6(16), 2894-2851).
The synthesis of deoxyribo-dinucleotides containing a cyclic phosphate internucleoside linkage and their incorporation into oligomeric compounds has been described. The Tm values of the duplexes with their DNA or RNA complements have also been reported (see Dupouy et al., Angew. Chem. Int. Ed., 2006, 45, 3623-3627).
The synthesis of DNA with cyclic phosphate internucleoside linkages to study the effect such linkages would have on polymerase chain reaction (PCR, see Martinez et al., PLoS ONE, 2011, 6(10), published online, 1-8).